The present invention is a method for producing an attenuation correction sinogram for a PET scanner and a positron gun for practicing this method. More particularly, a positron gun is mounted to the PET scanner to illuminate a patient in the scanner with positrons, a calibration sinogram is acquired from the resulting annihilation events and back projected to form a calibration image that depicts the boundaries between structures in the patient having different attenuation values. Attenuation values are assigned to these different structures and the resulting attenuation image is forward projected to form an attenuation sinogram used to correct acquired emission images of the patient.
The positron gun includes a source of positrons such as Na-22 contained in a housing which directs a beam of positrons out an opening in one end. The size of this beam may be adjusted and the positron gun is mounted on the PET scanner and transported around the patient to illuminate all surfaces.
A general object of the invention is to accurately correct an emission image acquired on a PET scanner. The calibration sinogram acquired using the positron gun is obtained very quickly after the images to be corrected have been acquired. This calibration data very precisely locates the boundaries of different structures and enables a more accurate and noise free attenuation correction sinogram to be computed.
The foregoing and other objects and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention, however, and reference is made therefore to the claims herein for interpreting the scope of the invention.